IBM AN/FSQ-31 SAC Data Processing System

US Air Force command, control, and coordination system

The IBM AN/FSQ 31 SAC Data Processing System (FSQ 31, Q 31, colloq.) was a USAF command, control, and coordination system for the Cold War Strategic Air Command (SAC). IBM's Federal Systems Division was the prime contractor for the AN/FSQ 31s, which were part of the TBD 465L SAC Automated Command and Control System (SACCS), a "Big L" system of systems (cf. 416L SAGE & 474L BMEWS) which had numerous sites throughout the Continental United States: "all SAC command posts and missile Launch Control Centers" (e. g., The Notch), a communication network, etc. ; and the several FSQ 31 sites including:
Offutt AFB's "Headquarters SAC Command Center" (DPC 1 & DPC 2 units)
Combat Operations Center, Fifteenth Air Force, at March AFB (DPC 3),
Barksdale AFB by March 1983. The FSQ 31 provided data to a site's Data Display Central (DDC) "a wall display" (e. g., Iconorama), and it arrived at Offutt in 1960. On 20 February 1987, "SAC declared initial operational capability for the SAC Digital Network [which] upgraded the SAC Automated Command and Control system "

The Q 31s were equipped with four 16 kiloword memory banks. The memory bank was oil and water cooled. Also considered as part of the memory subsystem in that they were addressed via fixed reserved memory addresses, were four 48 position switch banks, in which a short program could be inserted, and a plugboard, similar to the one used in IBM unit record equipment, that had the capacity of 32 words, so longer bootstrap or diagnostic programs could be installed in plug panels which could then be inserted into the receptacle and used. This served as a primitive ROM.